Electric power shovels

Abstract

The present application provides an electric power machine capable of suppressing an increase in component mounting area and the number of components to be mounted caused by high reliability required for ensuring current measurement. The electric power machine is provided with a motor, a shunt resistor, a current measurement unit, and a reference voltage supply unit. The shunt resistor is provided on a current path provided between a power supply and the motor. The current measurement unit measures a current flowing through the shunt resistor and outputs an output voltage of a voltage value corresponding to the measured current value. The reference voltage supply unit supplies a reference voltage set to be different from 0 V to the current measurement unit. The current measurement unit outputs the output voltage in a manner consistent with the reference voltage when no current flows through the shunt resistor. The reference voltage supply unit changes the voltage value of the reference voltage when a pre-set voltage change condition is satisfied.

Description

Technical Field

[0001] This invention relates to electric work machines. Background Technology

[0002] The electric work machine described in Patent Document 1 includes a current measuring circuit. The current measuring circuit measures the voltage across a resistor connected in series with the energized path on the negative side of the motor in order to determine the magnitude of the current supplied to the motor.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application No. 2019-123027 Summary of the Invention

[0006] To ensure high reliability of current measurement in electric work machines, two independent current measurement circuits can be used to compare their measurements.

[0007] However, since two current measurement circuits need to be installed, the component mounting area and the number of components are doubled compared to the case where the reliability of current measurement is not required.

[0008] One objective of this invention is to suppress the increase in component mounting area and the number of mounted components caused by the need to ensure the high reliability required for current measurement.

[0009] One aspect of the present invention is an electric work machine comprising: a motor, a shunt resistor, a current measuring unit, and a reference voltage supply unit.

[0010] The motor is configured to receive power from a power source for driving. A shunt resistor is placed in the current path between the power source and the motor to supply power from the power source.

[0011] The current measuring unit is configured to measure the magnitude of the current flowing through the shunt resistor and output an output voltage corresponding to the magnitude of the measured current.

[0012] The reference voltage supply unit is configured to supply a reference voltage that is set to be different from 0V to the current measuring unit.

[0013] The current measuring unit is configured to output an output voltage in a manner consistent with the reference voltage when no current flows through the shunt resistor.

[0014] The reference voltage supply unit is configured to change the value of the reference voltage when a preset voltage change condition is met.

[0015] For the electric work machine of the present invention configured in this way, when the voltage change condition is met and the reference voltage supply unit changes the value of the reference voltage, the current measuring unit can be judged to be normal when the output voltage value of the current measuring unit changes accordingly. Therefore, the electric work machine of the present invention does not require two independent current measuring units to ensure the high reliability required for current measurement. Furthermore, the circuit in the reference voltage supply unit for changing the value of the reference voltage can be configured with a simple circuit.

[0016] Accordingly, the electric working machine of the present invention can suppress the increase in component mounting area and number of mounted components caused by the high reliability required to ensure current measurement.

[0017] The output voltage value when the voltage change condition is met can be greater than the output voltage value when the voltage change condition is not met. Therefore, even if the reference voltage changes for some reason during the rotation of the motor of the electric work machine, the current measuring unit will output an output voltage that is larger than the output voltage equivalent to the actual current flowing through the shunt resistor.

[0018] Therefore, the electric operation function of the present invention can suppress the situation where, when an abnormality occurs such as a change in the reference voltage during the rotation of the motor of the electric operation machine, the current measurement is lower than the actual current value.

[0019] The electric work machine may be equipped with an overcurrent detection unit, which is configured such that when the output voltage is above a preset overcurrent detection threshold, it is determined that an overcurrent has been detected in the shunt resistor, and the value of the reference voltage when the voltage change condition is met is greater than the overcurrent detection threshold.

[0020] Accordingly, when the voltage change condition is met and the reference voltage supply unit changes the value of the reference voltage, the output voltage value of the changed current measuring unit is greater than the overcurrent detection threshold, and the overcurrent detection unit determines that an overcurrent has been detected. Therefore, the electric work machine of the present invention can simultaneously perform diagnosis (i.e., operation confirmation) of both the current measuring unit and the overcurrent detection unit by changing the value of the reference voltage.

[0021] Furthermore, the electric operation function of the present invention can suppress the following situation: when an abnormality occurs, such as a change in the reference voltage during the rotation of the motor of the electric operation machine, it is determined that an overcurrent has been detected, but the normal motor rotation process continues even though the abnormality has occurred.

[0022] The electric work machine may be equipped with a self-diagnostic unit, which is configured to perform a self-diagnosis based on the output voltage when a voltage change condition is met, to determine whether the current measuring unit has malfunctioned. Furthermore, the voltage change condition is met when the operating unit, configured to be operated by the user to make the electric work machine work, is not operated. If, during the self-diagnosis process, the self-diagnosis unit changes from a non-operational state where the operating unit is not operated to an operational state where the operating unit is operated, the self-diagnosis can be interrupted.

[0023] Accordingly, the electric operation function of the present invention can suppress the occurrence of a situation where the self-diagnosis of the current measuring unit is performed even when it is not possible to perform the self-diagnosis, thereby improving the diagnostic accuracy of the current measuring unit. Attached Figure Description

[0024] Figure 1 It is a three-dimensional diagram showing the overall structure of the electric work machine.

[0025] Figure 2 This is a block diagram showing the electrical configuration of an electric work machine.

[0026] Figure 3 This is a flowchart representing the control and processing of the work machine.

[0027] Figure 4 This is a flowchart representing the first half of the current sensor inspection and processing.

[0028] Figure 5 This is a flowchart showing the latter half of the current sensor inspection and processing.

[0029] Figure 6 It is a graph showing how the output voltage changes as the resistance value changes.

[0030] Figure 7 This is a circuit diagram of a reference voltage circuit with a shunt regulator.

[0031] Figure 8 This is a circuit diagram of a reference voltage circuit with a linear regulator.

[0032] Figure 9 It is a circuit diagram of a reference voltage circuit with an operational amplifier.

[0033] Explanation of symbols in attached drawings

[0034] 1… Electric work machine, 11… Motor, 23… Current measuring circuit, 24… Reference voltage circuit, R0… Resistor. Detailed Implementation

[0035] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 Please provide an explanation.

[0036] like Figure 1 As shown, the electric cutting machine 1 in this embodiment is a circular saw used to cut the workpiece.

[0037] The electric cutting machine 1 includes a base 2 and a main body 3. The base 2 is a generally rectangular component that contacts the upper surface of the workpiece being cut during the cutting operation. The main body 3 is disposed on the upper surface side of the base 2.

[0038] The main body 3 includes a circular saw blade 4, a saw blade housing 5, and a cover 6. The saw blade 4 is positioned on the right side of the main body 3 in the cutting direction. The saw blade housing 5 is formed such that approximately half of the periphery of the upper side of the saw blade 4 is housed inside and covered.

[0039] The cover 6 is formed to cover approximately half of the periphery of the underside of the saw blade 4. The cover 6 is an openable / closable type. Figure 1 The diagram shows the closed state of cover 6. During the cutting of the workpiece, by moving the electric cutting machine 1 in the cutting forward direction, cover 6 is moved along the center of rotation of the saw blade 4. Figure 1 The saw blade 4 gradually opens by rotating counterclockwise. This exposes the saw blade 4, and its exposed portion cuts into the workpiece.

[0040] A generally cylindrical motor housing 7 is provided on the left side of the main body 3. Inside this motor housing 7 is a motor 11, which serves as the drive source for the electric work machine 1. It should be noted that the motor 11 is shown in... Figure 2 And not shown Figure 1 .

[0041] A gear mechanism (not shown) is housed between the motor housing 7 and the saw blade 4. When the motor 11 rotates, the rotation is transmitted to the saw blade 4 via the gear mechanism, causing the saw blade 4 to rotate.

[0042] A handle 8, held by the user of the electric work machine 1, is disposed on the upper side of the main body 3. The handle 8 is mounted in an arch shape on the upper side of the main body 3. That is, the handle 8 is configured such that: the first end is fixed to the rear end side of the main body 3 in the cutting forward direction, and the second end is fixed to a position further forward in the cutting forward direction than the rear end.

[0043] A trigger switch 9 is installed on the handle 8. The user of the electric work machine 1 can pull and return the trigger switch 9 while holding the handle 8. It should be noted that the user of the electric work machine 1 can pull the trigger switch 9 by operating the locking lever that protrudes to the left or right of the handle 8 near the trigger switch 9. Specifically, the user of the electric work machine 1 can pull the trigger switch 9 by pressing the locking lever from the left or right side. Hereinafter, the state in which the trigger switch 9 is pulled is referred to as the on state, and the state in which the trigger switch 9 is returned is referred to as the off state.

[0044] At the rear end of the main body 3, a battery pack 10 is detachably mounted, housing a rechargeable battery 12. With the battery pack 10 mounted on the main body 3, pulling the trigger switch 9 will cause the motor 11 inside the main body 3 to rotate using power from the battery 12. It should be noted that the battery 12 is shown in... Figure 2 And not shown Figure 1 .

[0045] like Figure 2 As shown, the electric work machine 1 has a control unit 20.

[0046] The control unit 20 receives power from the battery 12 in the battery pack 10 to drive the motor 11. In this embodiment, the motor 11 is a 3-phase brushless motor.

[0047] The control unit 20 includes: a motor driver 21, a control circuit 22, a current measuring circuit 23, a reference voltage circuit 24, an overcurrent detection circuit 25, a latching circuit 26, a switch operation circuit 27, an overcurrent cutoff circuit 28, a power supply line 29, and a ground wire 30.

[0048] Power line 29 is the current path from the positive terminal PE of battery 12 through motor driver 21 to motor 11. Ground line 30 is the current path from the negative terminal NE of battery 12 through ground and motor driver 21 to motor 11.

[0049] The motor driver 21 is a circuit that receives power from the battery 12 via the power line 29 and the ground line 30, allowing current to flow through each phase winding of the motor 11. In this embodiment, the motor driver 21 includes a three-phase full-bridge circuit with six switching elements.

[0050] According to the control signal output from the control circuit 22, the motor driver 21 puts each switching element in the motor driver 21 into the on state or the off state, thereby allowing current to flow through each phase winding of the motor 11, causing the motor 11 to rotate.

[0051] The control circuit 22 includes a microcomputer equipped with a CPU 22a, ROM 22b, and RAM 22c. The various functions of the microcomputer are implemented by the CPU 22a executing programs stored in a non-transitional physical recording medium. In this example, the ROM 22b is a non-transitional physical recording medium storing programs. Furthermore, methods corresponding to the programs are executed by executing these programs. It should be noted that one or more ICs can be used to construct, from a hardware perspective, part or all of the functions performed by the CPU 22a. Additionally, the control circuit 22 may include multiple microcomputers.

[0052] The current measuring circuit 23 includes resistors R0, R1, R2, R3, R4 and operational amplifier A1.

[0053] Resistor R0 is a shunt resistor and is set on ground wire 30.

[0054] The first terminal of resistor R1 is connected to the end of resistor R0 on the motor driver 21 side. The second terminal of resistor R1 is connected to the non-inverting input terminal of operational amplifier A1.

[0055] The first terminal of resistor R2 is connected to the ground side of resistor R0. The second terminal of resistor R2 is connected to the inverting input terminal of operational amplifier A1.

[0056] The first terminal of resistor R3 is connected to the inverting input terminal of operational amplifier A1. The second terminal of resistor R3 is connected to the output terminal of operational amplifier A1.

[0057] The first terminal of resistor R4 is connected to the non-inverting input terminal of operational amplifier A1. The second terminal of resistor R4 is connected to the reference voltage circuit 24.

[0058] The resistance value of resistor R1 is equal to that of resistor R2. The resistance value of resistor R3 is equal to that of resistor R4. In this embodiment, the resistance values ​​of resistors R1 and R3 are 10kΩ or less. This is because it avoids the influence of stray capacitance and ensures accurate output for high-speed input signal changes.

[0059] The output terminal of operational amplifier A1 is connected to the A / D input port P1 of control circuit 22 via resistor R11.

[0060] The current measuring circuit 23 configured in this way will output the voltage V shown in equation (1). out Output from the output terminal of operational amplifier A1. V1 in equation (1) is the voltage value at the first terminal of resistor R1. V2 in equation (1) is the voltage value at the first terminal of resistor R2. R1 in equation (1) is the resistance value of resistor R1. R3 in equation (1) is the resistance value of resistor R3. V in equation (1)ref The voltage value is the reference voltage output from the reference voltage circuit 24. In this embodiment, the gain (i.e., R3 / R1) of the current measuring circuit 23 is set to 20 or less. This is because if the gain of the current measuring circuit 23 is made greater than or equal to the open-loop gain of the operational amplifier A1 at its speed in order to cope with high-speed input signal changes, the input waveform cannot be reproduced in the operational amplifier A1.

[0061] V out = (V1-V2)×(R3 / R1)+V ref ···(1)

[0062] The reference voltage circuit 24 includes resistors R5 and R6 and a PNP transistor T1.

[0063] A 5V voltage is applied to the first terminal of resistor R5. The second terminal of resistor R5 is connected to the first terminal of resistor R6, and this connection point is the output of reference voltage circuit 24. The second terminal of resistor R6 is grounded. In this embodiment, the resistance value of resistor R5 is equal to the resistance value of resistor R6.

[0064] The base of PNP transistor T1 is connected to the output port P2 of control circuit 22. A 5V voltage is applied to the emitter of PNP transistor T1. The collector of PNP transistor T1 is connected to the junction between resistors R5 and R6.

[0065] Alternatively, the collector of the PNP transistor T1 can be connected to the junction between resistors R5 and R6 via a resistor. In this case, the reference voltage value for turning on the PNP transistor T1 can be arbitrarily set by the resistance value of the resistors involved. The set voltage can be set to a value higher than the overcurrent detection threshold of the overcurrent detection circuit 25 set in resistors R7 and R8 (described later). In this case, when the PNP transistor T1 is turned on, the overcurrent detection circuit 25 (described later) can operate. It can be seen that if at least the set voltage value, that is, at least a current equivalent to the set voltage value, flows through resistor R0, the overcurrent detection circuit 25 can operate.

[0066] The resistance values ​​of resistors R5 and R6 are set in the manner of "(resistance value of resistor R1) >> (resistance values ​​of resistors R5 and R6)". This is because making the output impedance of the reference voltage circuit 24 at least 1 / 10 of the resistance value of resistor R1 can reduce the influence of the output impedance on the current measuring circuit 23.

[0067] The reference voltage circuit 24 configured in this way outputs a reference voltage V of 2.5V when the PNP transistor T1 is in the off state. refWhen the PNP transistor T1 is in the ON state, it outputs a 5V reference voltage V. ref .

[0068] The overcurrent detection circuit 25 includes: resistors R7, R8, R9, R10, capacitors C1 and C2, and comparator A2.

[0069] A 5V voltage is applied to the first terminal of resistor R7. The second terminal of resistor R7 is connected to the first terminal of resistor R8 and the inverting input terminal of comparator A2. The second terminal of resistor R8 is grounded.

[0070] The first terminal of resistor R9 is connected to the output terminal of operational amplifier A1. The second terminal of resistor R9 is connected to the non-inverting input terminal of comparator A2.

[0071] The first terminal of resistor R10 is connected to latch-up circuit 26. The second terminal of resistor R10 is connected to the non-inverting input terminal of comparator A2.

[0072] A 5V voltage is applied to the first terminal of capacitor C1. The second terminal of capacitor C1 is connected to the inverting input terminal of comparator A2. The first terminal of capacitor C2 is connected to the non-inverting input terminal of comparator A2. The second terminal of capacitor C2 is grounded.

[0073] The low-pass filter on the non-inverting input terminal side of comparator A2 is formed by resistor R9 and capacitor C2.

[0074] The purpose of capacitor C1 is to form a low-pass filter on the inverting input terminal side of comparator A2. Additionally, when an external 5V voltage is applied, capacitors C1 and C2 can keep the output of comparator A2 fixed at a low level.

[0075] The time constant of the low-pass filter on the non-inverting input terminal side of comparator A2 (i.e., the product of the resistance value of resistor R9 and the capacitance of capacitor C2) is set to less than 1μs to enable the overcurrent detection circuit 25 to respond quickly.

[0076] In this configuration, the overcurrent detection circuit 25 outputs a high-level signal as an overcurrent signal from the output terminal of comparator A2 when the voltage at the non-inverting input terminal of comparator A2 (i.e., the voltage at the output terminal of operational amplifier A1) is greater than the voltage at the inverting input terminal of comparator A2. In other words, the voltage applied to the inverting input terminal of comparator A2 is the overcurrent detection threshold.

[0077] The latching circuit 26 includes a PNP transistor T2 and an NPN transistor T3.

[0078] The base of PNP transistor T2 is connected to the collector of NPN transistor T3.

[0079] The emitter of the PNP transistor T2 is connected to the output port P3 of the control circuit 22 via diode D1. It should be noted that the anode of diode D1 is connected to the output port P3 of the control circuit 22, and the cathode of diode D1 is connected to the emitter of the PNP transistor T2. Furthermore, the emitter of the PNP transistor T2 is connected to the switching operation circuit 27 via diode D2.

[0080] The collector of PNP transistor T2 is connected to the non-inverting input terminal of comparator A2 via resistor R10.

[0081] The base of NPN transistor T3 is connected to the output terminal of comparator A2. The emitter of NPN transistor T3 is grounded. The collector of NPN transistor T3 is connected to the input port P4 of control circuit 22.

[0082] In the latching circuit 26 configured as described above, when a high level is output from the output port P3 of the control circuit 22 or a high level is output from the switch operation circuit 27, if an overcurrent signal is output from the output terminal of comparator A2, then PNP transistor T2 and NPN transistor T3 are turned on, and the non-inverting input terminal of comparator A2 is pulled up to a high level by means of resistor R10. Then, even if the voltage value of the signal output from the output terminal of operational amplifier A1 decreases, the non-inverting input terminal of comparator A2 will still be pulled up, therefore, the output of comparator A2 remains unchanged, and the turned-on state of PNP transistor T2 and NPN transistor T3 is maintained. Furthermore, the turned-on state of PNP transistor T2 and NPN transistor T3 continues until the trigger switch 9 switches from the on state to the off state, or until the output port P3 of the control circuit 22 switches from a high level to a low level.

[0083] The switching operation circuit 27 is equipped with a PNP transistor T4.

[0084] The base of PNP transistor T4 is connected to trigger switch 9. A 5V voltage is applied to the emitter of PNP transistor T4. The collector of PNP transistor T4, the anode of diode D2, and the input port P5 of control circuit 22 are connected. The cathode of diode D2 is connected to the emitter of PNP transistor T2.

[0085] In a switching circuit 27 configured as described above, if the trigger switch 9 switches from the off state to the on state, the base of the PNP transistor T4 becomes grounded, and the PNP transistor T4 is in the on state. Accordingly, the switching circuit 27 outputs a 5V voltage.

[0086] An overcurrent cutoff circuit 28 is provided on the power supply line 29. Furthermore, the overcurrent cutoff circuit 28 switches between an on state (connecting the current path) and an off state (cutting off the current path) based on an externally input overcurrent control signal. It should be noted that the overcurrent control signal is the collector voltage level of the NPN transistor T3.

[0087] The overcurrent cutoff circuit 28 is in the ON state when the overcurrent control signal is high and in the OFF state when the overcurrent control signal is low.

[0088] Next, the steps of the machine control processing executed by the CPU 22a of the control circuit 22 will be explained. The machine control processing is the process that begins after the control circuit 22 is started by supplying a 5V voltage to it.

[0089] When executing machine control processing, such as Figure 3 As shown, CPU22a first performs the following in S10: initialization, which sets the various parameters used in the machine control processing to their initial values.

[0090] Then, in S20, CPU22a determines whether trigger switch 9 is in the off state. Specifically, if the voltage level of input port P5 is high, CPU22a determines that trigger switch 9 is in the on state; if the voltage level of input port P5 is not high, CPU22a determines that trigger switch 9 is in the off state.

[0091] Here, with the trigger switch 9 in the ON state, the system enters standby mode by repeatedly performing the S20 process until the trigger switch 9 becomes OFF.

[0092] Then, when the trigger switch 9 is turned off, the CPU 22a performs various checks in S30. For example, the CPU 22a checks the voltage of the battery 12 or the temperature of the switching element of the motor driver 21.

[0093] Then, CPU22a performs the current sensor check process described later in S40.

[0094] After the current sensor check is completed, CPU22a determines in S50 whether the current sensor error flag F1 (described later) has been set. It should be noted that setting the flag means setting its value to 1; clearing the flag means setting its value to 0. Here, if the current sensor error flag F1 is cleared, CPU22a determines in S60 whether the trigger switch 9 is in the ON state. Here, if the trigger switch 9 is in the OFF state, the process in S60 is repeated to enter standby mode until the trigger switch 9 becomes ON.

[0095] Then, when the trigger switch 9 becomes on, the CPU 22a executes motor drive processing for driving the motor 11 in S70, and enters S60.

[0096] In addition, if the current sensor error flag F1 is set in S50, the CPU22a executes the prescribed error handling in S80 and terminates the machine control processing.

[0097] Next, the steps of the current sensor inspection process executed by CPU22a in S40 will be explained.

[0098] When performing current sensor check processing, such as Figure 4 As shown, CPU 22a first determines in S110 whether trigger switch 9 is in the off state. Here, if trigger switch 9 is in the on state, CPU 22a completes the current sensor check process. On the other hand, if trigger switch 9 is in the off state, CPU 22a reads in S120 the output voltage V from current measuring circuit 23. out .

[0099] Then, in S130, CPU22a bases its output voltage V on the input voltage. out This is used to determine whether the drive current value is 0A. Specifically, the output voltage V... out Within the preset normal voltage range, CPU22a determines the drive current value to be 0A; the output voltage V out If the voltage is outside the normal range, the CPU22a determines that the drive current value is not 0A. In this embodiment, the normal voltage range is between 2.4V and 2.6V.

[0100] Here, if the drive current value is not 0A, CPU22a enters S280. On the other hand, if the drive current value is 0A, CPU22a outputs a virtual switch on signal in S140. Specifically, CPU22a sets the voltage of output port P3 to a high level.

[0101] Then, in S150, CPU22a determines whether trigger switch 9 is in the off state. If trigger switch 9 is in the on state, CPU22a stops the output of the virtual switch on signal in S160. Specifically, CPU22a sets the voltage of output port P3 to a low level.

[0102] Then, in S170, CPU22a determines whether trigger switch 9 is in the ON state. Here, if trigger switch 9 is in the ON state, CPU22a finishes the current sensor check process. On the other hand, if trigger switch 9 is in the OFF state, CPU22a proceeds to S280.

[0103] Furthermore, in S150, when the trigger switch 9 is in the off state, the CPU22a determines in S180 whether an overcurrent has been detected. Specifically, when the voltage level of the input port P4 is low, the CPU22a determines that "an overcurrent has been detected".

[0104] Here, if an overcurrent is detected, CPU22a enters S280. On the other hand, if no overcurrent is detected, CPU22a outputs a reference voltage change signal in S190. Specifically, CPU22a sets the voltage at output port P2 to a low level.

[0105] Then, CPU22a reads the output voltage V in S200. out Then, as Figure 5 As shown, CPU22a determines in S210: the read output voltage V out Is the value equal to the value of the changed reference voltage (i.e., 5V)?

[0106] Here, the output voltage V out If the value of the voltage is not equal to the value of the changed reference voltage, CPU22a enters S280. On the other hand, the output voltage V... out If the value is equal to the value of the changed reference voltage, CPU22a, in S220, similarly to S180, determines whether an overcurrent has been detected.

[0107] Here, if no overcurrent is detected, CPU22a enters S280. On the other hand, if an overcurrent is detected, CPU22a stops the output of the reference voltage change signal in S230. Specifically, CPU22a sets the voltage of output port P2 to a high level.

[0108] Next, in S240, CPU22a, similar to S180, determines whether an overcurrent has been detected. If no overcurrent is detected, CPU22a proceeds to S280. On the other hand, if an overcurrent is detected, CPU22a stops the output of the virtual switch on signal in S250. Specifically, CPU22a sets the voltage at output port P3 to a low level.

[0109] Then, in S260, CPU22a, similarly to S180, determines whether an overcurrent has been detected. If no overcurrent is detected, CPU22a terminates the current sensor check process. On the other hand, if an overcurrent is detected, CPU22a determines in S270 whether trigger switch 9 is in the ON state. If trigger switch 9 is in the ON state, CPU22a terminates the current sensor check process. If trigger switch 9 is in the OFF state, CPU22a proceeds to S280.

[0110] Upon entering S280, CPU22a sets the current sensor error flag F1 configured in RAM22c and ends the current sensor check process.

[0111] Figure 6 This indicates the output voltage V when the drive current is 0A. out This graph shows the changes in voltage as the resistance values ​​of resistors R1, R2, R3, R4, R5, and R6 change. Lines L1, L2, L3, L4, L5, and L6 represent the output voltage V. out The change occurs as the resistance values ​​of resistors R1, R2, R3, R4, R5, and R6 change.

[0112] The normal resistance values ​​of resistors R1, R2, R3, R4, R5, and R6 are 4.7kΩ, 100kΩ, 4.7kΩ, 100kΩ, 100Ω, and 100Ω, respectively.

[0113] like Figure 6 As shown, when the drive current is 0A, if the resistance value of one of the resistors R1, R2, R3, R4, R5, and R6 changes, the output voltage V will change. out The voltage deviates from 2.5V. Therefore, the normal voltage range mentioned above is above 2.4V and below 2.6V.

[0114] The electric work machine 1 configured in this way includes: a motor 11, a resistor R0, a current measuring circuit 23, and a reference voltage circuit 24.

[0115] Motor 11 is driven by power supplied from battery 12. Resistor R0 is connected to ground wire 30, which is provided between battery 12 and motor 11 to supply power from battery 12 to motor 11. Resistor R0 is a shunt resistor. Current measuring circuit 23 measures the magnitude of the current flowing through resistor R0 and outputs an output voltage V corresponding to the measured current magnitude. out The reference voltage circuit 24 supplies the current measuring circuit 23 with a reference voltage V that is set to be different from 0V. ref .

[0116] The current measuring circuit 23 outputs an output voltage V in a manner consistent with the reference voltage when no current flows through the resistor R0. out When the preset voltage change conditions are met, the reference voltage circuit 24 adjusts the reference voltage V. ref The value is changed. The voltage change condition is met when the trigger switch 9 is in the open state immediately after the control circuit 22 is started.

[0117] In this way, for the electric work machine 1, the reference voltage circuit 24 adjusts the reference voltage V by the voltage change condition being met. ref When the value is changed, the output voltage V of the current measuring circuit 23... out When the value changes accordingly, it can be determined that the current measuring circuit 23 is functioning normally. Therefore, the electric work machine 1, which requires high reliability in current measurement, does not need to have two independent current measuring circuits 23 to ensure this reliability. Furthermore, the reference voltage circuit 24 is used to measure the reference voltage V. ref The circuit that changes the value can be set up as a simple circuit.

[0118] Accordingly, the electric working machine 1 can suppress the increase in component mounting area and number of mounted components caused by the high reliability required to ensure current measurement.

[0119] In addition, the output voltage V when the voltage change condition is met out The value can be greater than the output voltage V when the voltage change condition is not met. out The value of V. Therefore, even if the reference voltage V is reduced for some reason during the rotation of the motor 11 of the electric work machine 1. ref In the event of a change, the current measuring circuit 23 will also output an output voltage V that is equivalent to the actual current flowing through resistor R0. out A larger output voltage V is also needed. out .

[0120] Therefore, the electric work machine 1 can suppress the following situation: when the reference voltage V is generated during the rotation of the motor 11 of the electric work machine 1... ref In cases of abnormal changes, the current measurement may be lower than the actual current value.

[0121] In addition, the overcurrent detection circuit 25 outputs voltage V out If the current exceeds a pre-set overcurrent detection threshold, it is determined that an overcurrent has been detected in resistor R0. Furthermore, the reference voltage V when the voltage change condition is met... ref The value is greater than the overcurrent detection threshold.

[0122] Accordingly, when the voltage change condition is met, the reference voltage circuit 24 sets the reference voltage V. ref If the value is changed, the output voltage V of the changed current measuring circuit 23 out The value is greater than the overcurrent detection threshold, and the overcurrent detection circuit 25 determines that an overcurrent has been detected. Therefore, the electric work machine 1 activates the reference voltage V. ref By changing the value, it is possible to simultaneously diagnose (i.e., confirm the action) both the current measuring circuit 23 and the overcurrent detection circuit 25.

[0123] Control circuit 22 performs self-diagnosis, that is, based on the output voltage V when the voltage change condition is met. out The system determines whether the current measuring circuit 23 is malfunctioning. Furthermore, if the voltage change condition is met when the trigger switch 9, which is operated by the user to operate the electric work machine 1, is not activated, the control circuit 22 will interrupt the self-diagnosis process if it changes from a non-operational state (where the control circuit 22 is not operated) to an operational state (where the control circuit 22 is operated).

[0124] Accordingly, the electric working machine 1 can suppress the occurrence of a situation where it performs self-diagnosis even though it cannot perform self-diagnosis of the current measuring circuit 23, thereby improving the diagnostic accuracy of the current measuring circuit 23.

[0125] In the embodiments described above, resistor R0 corresponds to an example of a shunt resistor in the present invention, current measuring circuit 23 corresponds to an example of a current measuring unit in the present invention, reference voltage circuit 24 corresponds to an example of a reference voltage supply unit in the present invention, and overcurrent detection circuit 25 corresponds to an example of an overcurrent detection unit in the present invention.

[0126] In addition, the battery 12 is equivalent to an example of the power source in this invention, and the ground wire 30 is equivalent to an example of the current path in this invention.

[0127] Furthermore, S210 corresponds to an example of the self-diagnosis unit in this invention, and the trigger switch 9 corresponds to an example of the operation unit in this invention.

[0128] While one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and can be modified and implemented in various ways.

[0129] For example, the above embodiment provides a scheme in which the reference voltage circuit 24 includes resistors R5 and R6 and a PNP transistor T1. However, as... Figure 7 As shown, the reference voltage circuit 24 may include: resistors R5, R6, R21, R22, capacitor C21, NPN transistor T21, and shunt regulator SR.

[0130] A 5V voltage is applied to the first terminal of resistor R21. The second terminal of resistor R21 is connected to the first terminal of resistor R5. The second terminal of resistor R5 is connected to the first terminals of resistors R6 and R22. The second terminal of resistor R6 is grounded.

[0131] The first terminal of capacitor C21 is connected to the junction between resistors R21 and R5. The second terminal of capacitor C21 is grounded.

[0132] The base of NPN transistor T21 is connected to the output port P2 of control circuit 22. The collector of NPN transistor T21 is connected to the second end of resistor R22. The emitter of NPN transistor T21 is grounded.

[0133] The cathode of the shunt regulator SR is connected to the connection point between resistors R21 and R5. The anode of the shunt regulator SR is grounded. The reference terminal of the shunt regulator SR is connected to the connection point between resistors R5 and R6.

[0134] Furthermore, the reference voltage circuit 24 uses the cathode voltage at the connection point between resistor R21 and shunt regulator SR as the reference voltage V. ref Output.

[0135] In the reference voltage circuit 24 configured as shown, the voltage at the connection point between resistors R5 and R6 is input to the reference terminal of the shunt regulator SR. The shunt regulator SR generates a cathode voltage in such a way that the voltage input to the reference terminal reaches a specified voltage, and this voltage serves as the reference voltage V. ref Output. It should be noted that when the NPN transistor T21 is in the ON state, the voltage input to the reference terminal is determined by resistors R5, R6, and R22. Conversely, when the NPN transistor T21 is in the OFF state, the voltage input to the reference terminal is determined by resistors R5 and R6.

[0136] In addition, such as Figure 8 As shown, the reference voltage circuit 24 may include: resistors R5, R6, R31, capacitor C31, NPN transistor T31, and variable output linear regulator LDO.

[0137] The first terminal of resistor R5 is connected to the output terminal V of the variable output linear regulator LDO. out Connections: The second terminal of resistor R5 is connected to the first terminals of resistors R6 and R31. The second terminal of resistor R6 is grounded. The second terminal of resistor R31 is connected to the collector of NPN transistor T31.

[0138] The first terminal of capacitor C31 is connected to the output terminal V of the variable output linear regulator LDO. out Connect. The second terminal of capacitor C31 is grounded.

[0139] The base of NPN transistor T31 is connected to the output port P2 of control circuit 22. The emitter of NPN transistor T31 is grounded.

[0140] A 5V voltage is applied to the input terminal Vdd of the variable output linear regulator (LDO). The feedback terminal FB of the LDO is connected to the connection point between resistors R5, R6, and R31. The ground terminal of the LDO is grounded.

[0141] In this reference voltage circuit 24, when the output port P2 is high, the NPN transistor T31 is turned on, and the voltage determined by resistors R5, R6, and R31 flows from the output terminal V. out Output. Additionally, when the reference voltage circuit 24 is at a low level at output port P2, the NPN transistor T31 is in the off state, allowing the voltage determined by resistors R5 and R6 to flow from the output terminal V. out Output.

[0142] In addition, such as Figure 9 As shown, the reference voltage circuit 24 may include: resistor R41 and operational amplifier A41.

[0143] The first terminal of resistor R41 is connected to the collector of PNP transistor T1. The second terminal of resistor R41 is connected to the junction between resistors R5 and R6.

[0144] The non-inverting input terminal of operational amplifier A41 is connected to the connection point between resistors R5 and R6. The inverting input terminal of operational amplifier A41 is connected to the output terminal of operational amplifier A41.

[0145] The reference voltage circuit 24 configured in this way can use the same voltage as the voltage at the connection point between resistors R5 and R6 as the reference voltage V. ref It outputs at low output impedance from the output terminal of operational amplifier A41.

[0146] Alternatively, the output port P2, which enables D / A conversion, can be connected to the non-inverting input terminal of the operational amplifier A1 in the current measurement circuit 23 via resistor R4, thus replacing the reference voltage circuit 24. That is, the reference voltage can be changed by switching the voltage level of the D / A conversion output port P2 between, for example, 2.5V and 5V.

[0147] The technology of this invention can be applied to various electric work machines, such as electric hammers, electric hammer drills, electric drills, electric screwdrivers, electric wrenches, electric grinders, electric circular saws, electric reciprocating saws, electric wire saws, electric cutting machines, electric chainsaws, electric planers, electric nailing machines (including riveting machines), electric hedge trimmers, electric lawn mowers, electric lawn shears, electric brush cutters, electric vacuum cleaners, electric blowers, electric sprayers, electric spreaders, electric dust collectors, and so on.

[0148] Multiple functions of one component in the above embodiments can be implemented by multiple components, or one function of one component can be implemented by multiple components. Alternatively, multiple functions of multiple components can be implemented by one component, or one function implemented by multiple components can be implemented by one component. Furthermore, a portion of the configuration in the above embodiments can be omitted. Additionally, at least a portion of the configuration in the above embodiments can be added to or substituted relative to the configurations of other above embodiments.

[0149] In addition to the electric work machine 1 described above, the present invention can also be implemented using various schemes such as a program that enables the computer to function as the control unit 20, a non-transitional physical recording medium such as a semiconductor memory that records the program, and an electric work machine control method.

Claims

1. An electric work machine, characterized in that, have: A motor configured to receive power from an electrical source for driving; The operating unit is configured to be operated by a user to make the electric work machine work; A shunt resistor is provided in the current path between the power source and the motor for supplying power from the power source to the motor; The current measuring unit is configured to measure the magnitude of the current flowing through the shunt resistor and output an output voltage corresponding to the magnitude of the measured current. as well as A reference voltage supply unit supplies a reference voltage, which is set to be different from 0V, to the current measuring unit. The current measuring unit is configured to output the output voltage in a manner consistent with the reference voltage when no current flows through the shunt resistor. The reference voltage supply unit is configured to change the value of the reference voltage when a preset voltage change condition is met. The voltage change condition is met when the operating unit is not operated.

2. The electric work machine according to claim 1, characterized in that, The output voltage value when the voltage change condition is met is greater than the output voltage value when the voltage change condition is not met.

3. The electric work machine according to claim 1 or 2, characterized in that, The electric work machine includes an overcurrent detection unit configured to determine that an overcurrent has been detected in the shunt resistor when the output voltage is above a preset overcurrent detection threshold. When the voltage change condition is met, the value of the reference voltage is greater than the overcurrent detection threshold.

4. The electric work machine according to claim 1 or 2, characterized in that, The electric work machine includes a self-diagnostic unit configured to perform a self-diagnostic function based on the output voltage when the voltage change condition is met, to determine whether the current measuring unit has generated an abnormality. The self-diagnosis unit is configured to interrupt the self-diagnosis process when the self-diagnosis process changes from a non-operational state where the operation unit is not operated to an operational state where the operation unit is operated.

Images